We are attempting to understand the regulated expression of the globulin and immunoglobulin genes. For this purpose we have cloned and determined the structure of and a physical map for both the mouse alpha and beta globin genes as well as the mouse kappa immunoglobulin genes. In so doing we have identified sites critical to the transcription, polyA addition and splicing of the mRNA precursors using both in vivo and in vitro assays. We have also discovered and determined the sequence of several globin pseudogenes, including one entirely lacking intervening sequences. We have also shown how immunoglobulin gene diversity must arise and tested various models to account for site specific immunoglobulin gene recombination and its role in generating immunoglobulin diversity.